Heat recuperation device for an exhaust line

ABSTRACT

The heat recuperation device for an exhaust line comprises
         a valve body having at least one exhaust gas inlet and at least one exhaust gas outlet.   A shutter element is able to move at least between a position of blocking off a cutoff section of a path along which the exhaust gases pass and an uncovering position.   The valve body has an inlet zone situated between the inlet and the cutoff section, and an outlet zone situated between the cutoff section and the outlet. The device further comprises a plurality of heat-exchange tubes, with each tube having an upstream end connected directly to the inlet zone, a downstream end connected directly to the outlet zone, and at least one curved portion between the upstream and downstream ends.

TECHNICAL FIELD

The invention generally relates to heat recuperation devices for exhaust lines.

More specifically, the invention relates to a heat recuperation device for an exhaust line, comprising: a valve body having at least one exhaust gas inlet and at least one exhaust gas outlet, the valve body inwardly defining a direct passage pathway for the exhaust gases from the inlet to the outlet; a shutter element positioned in the valve body, able to move relative to the valve body at least between a blocking off position in which the shutter blocks off a cutoff section of the path along which the exhaust gases pass and thereby prohibits the circulation of the exhaust gases from the inlet toward the outlet along the path, and an uncovering position, in which the shutter element frees said cutoff section of the path along which the exhaust gases pass and thereby allows the circulation of the exhaust gases from the inlet toward the outlet along the path.

BACKGROUND

It is known that to ensure the recuperation of part of the heat from the exhaust gases, two exhaust gas circulation ducts should be positioned in parallel, with a heat exchanger being inserted on one of the two ducts, and the other duct making it possible to bypass the exchanger. A valve including a valve body and a shutter element, of the type described above, is for example inserted in each of the two ducts so as to orient the exhaust gases either toward the exchanger or toward the bypass, as needed.

Such an assembly is complex, includes a large number of parts, and is very bulky.

In this context, the invention aims to propose a heat recuperation device that is more compact.

SUMMARY

A heat recuperation device of the aforementioned type includes a valve body that has an inlet zone situated along a passage pathway between an inlet and a cutoff section. An outlet zone is situated along the passage pathway between the cutoff section and the outlet. The device further comprises a plurality of heat exchange tubes provided for circulation of the exhaust gases, with each tube having an upstream end connected directly to the inlet zone and communicating with the passage pathway, a downstream end connected directly to the outlet zone and communicating with the passage pathway, and at least one curved portion between the upstream and downstream ends.

The device may also include one or more of the features below, considered individually according to any technically possible combinations:

a shutter prohibits the circulation of the exhaust gases in the heat exchange tubes in an uncovering position;

the shutter covers the upstream ends of the heat exchange tubes or the downstream ends of the heat exchange tubes in the uncovering position;

the heat exchange tubes are U-shaped tubes;

in each heat exchange tube, the curved portion(s) cover an angular sector comprised between 90° and 225°;

in each heat exchange tube, the upstream and downstream ends extend in a first plane, a central part of the heat exchange tubes extending in a second plane that is inclined relative to the first plane, the second plane preferably forming an angle comprised between 30° and 90° relative to the first plane;

the exhaust gases flow along the inlet and outlet zones in general respective directions, the upstream and downstream ends of the heat exchange tubes forming an angle comprised between 45° and 135° with said respective general directions;

the inlet and outlet zones are situated on the same side wall of the valve body, the shutter being rotatably mounted with respect to the valve body around an axis of rotation situated in the immediate vicinity of said side wall;

the device comprises an enclosure having a coolant inlet, a coolant outlet and an opening turned toward the valve body, the heat exchange tubes extending in the enclosure, the opening being defined by a peripheral edge sealably connected to the valve body around the inlet and outlet zones; and

the device comprises an enclosure having a coolant inlet, a coolant outlet and an opening turned toward the valve body, the device further comprising a wall covering the opening, the wall being passed through by the heat exchange tubes and not coming into direct contact with the valve body.

These and other features may be best understood from the following drawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will emerge from the detailed description thereof provided below, for information and non-limitingly, in reference to the appended Figures, in which:

FIG. 1 is a perspective view of a heat recuperation device according to the invention;

FIG. 2 is a perspective view of the device of FIG. 1, considered from a different angle, the enclosure of the heat exchanger not being shown to leave the tubes visible;

FIG. 3 is a perspective view of the device of FIG. 1, one of the two half-shells forming the valve body not being shown to leave the inside of the valve body visible;

FIG. 4 is a perspective view similar to that of FIG. 3, part of the enclosure of the heat exchanger not being shown, and the valve being shown in the blocking off position;

FIG. 5 is a perspective view of the valve body, similar to that of FIG. 2, the heat exchange tubes not being shown;

FIG. 6 is a perspective view of a second embodiment of the invention, in which the enclosure of the heat exchanger is isolated from the valve body by an air knife; and

FIG. 7 is a diagrammatic illustration of the heat exchange tube according to one alternative embodiment of the invention, in which the curved central portion of the tube is in a plane that is inclined relative to the ends of the tube.

DETAILED DESCRIPTION

The heat recuperation device of FIG. 1 is designed to be inserted in the exhaust line of a motor vehicle. This device is designed to recover part of the heat energy from the exhaust gases, for example to transfer it to the engine coolant, or the passenger compartment heating circuit.

The device 1 essentially includes a valve 3 and a heat exchanger 5.

The valve 3 includes a valve body 7, an exhaust gas inlet 9, and an exhaust gas outlet 11. The valve body inwardly defines a passage pathway 13 for the exhaust gases to pass directly from the inlet 9 to the outlet 11. A shutter element 15 is positioned inside the valve body 7, and is able to move relative to the valve body 7 between a blocking off position, in which the shutter element 15 blocks off a cutoff section of the path and thereby prohibits circulation of the exhaust gases from the inlet 9 to the outlet 11 along the path, and an uncovering position, in which the shutter element 15 uncovers said cutoff section and thereby allows the circulation of the exhaust gases from the inlet 9 to the outlet 11 along the path 13.

The shutter element 15 is able to rotate relative to the valve body between its blocking off and uncovering positions, around an axle 17 shown in FIGS. 2, 4 and 5. The axle 17 is mounted freely rotating on the valve body by guide bearings such as the bearing 19 shown in FIG. 1. The shutter element 15 is secured to the axle 17.

One end 21 of the axle 17 protrudes outside the valve body 7 and is rigidly fixed to a crank 23. The crank 23 is provided to be connected to an actuator, for example driven by a computer, and provided to move the valve between its different positions.

The valve body 7 includes two half-shells 25, 27 alongside one another by respective edges 29. The edges 29 are alongside one another, against one another, along a contact plane substantially parallel to the axle 17. Half of the inlet 9 and the outlet 11 are each defined by the half-shell 25, and the other half by the half-shell 27.

The axle 17 is mounted on the half-shell 27.

As shown in FIG. 3, the valve 3 also includes a frame 31, placed inside the valve body 7 and secured to the half-shells 25 and 27. The frame 31 defines a sealing step for the shutter element 15 in the blocking off position thereof. It also defines the cutoff section. Its entire periphery is pressed against the inner wall of the valve body 7, and inwardly defines a passage opening for the exhaust gases that is closed off by the shutter element 15 in its blocking off position.

As shown in FIGS. 3 and 5, the valve body 7 bears openings 33 over an exhaust gas inlet zone 35 into the heat exchanger 5. The valve body 7 has other openings 36 into an exhaust gas outlet zone 37 outside the heat exchanger 5.

The inlet zone 35 is situated, along the path 13, between the inlet 9 and the cutoff section defined by the frame 31. The inlet zone 35 is substantially planar.

The outlet zone 37 is situated, along the path 13, between the cutoff section and the outlet 11. The outlet zone 37 is substantially planar.

The inlet and outlet zones 35 and 37 are situated on the same side wall 39 of the valve body 7. They are situated substantially in the same plane.

The axle 17 is situated in the immediate vicinity of the wall 39. More specifically, the side wall 39 has, between the inlet and outlet zones 35, 37, a zone 41 (FIG. 2) protruding toward the outside of the valve body 7 relative to the inlet and outlet zones 35 and 37. The zone 41 has a substantially semi-cylindrical shape. The axle 17 is situated in the immediate vicinity of the protruding zone 41, such that the axle 17 extends substantially in the plane of the inlet 35 and outlet 37 zones.

The number of openings 33 of the inlet zone 35 is equal to the number of openings 36 of the outlet zone 37.

The heat exchanger 5 includes a plurality of heat exchange tubes 43 (FIG. 2) and an outer enclosure 44, the tubes 43 being placed in the outer enclosure 44.

Each tube 43 comprises an upstream end 45 directly connected to the inlet zone 35 of the valve body 7 and communicating with the passage pathway 13. It also comprises a downstream end 47 directly connected to the outlet zone 37 and communicating with the passage pathway 13. It further comprises at least one curved portion 49 between the upstream and downstream ends 45 and 47. The upstream end 45 of each tube 43 is engaged in one of the inlet openings 33 and is rigidly fixed to the inlet zone 35. It is, for example, laser welded to the peripheral edge of the opening 33 Likewise, the downstream end 47 is engaged in one of the outlet holes 36, and is rigidly fixed to the outlet zone 37. The downstream end 47 is, for example, laser welded to the peripheral edge of the opening 36.

In order to make the device 1 more compact, and to bring the inlet openings 33 as close as possible to the outlet openings 36, the curved portions 49 each cover an angular sector comprised between 90° and 225°, preferably comprised between 135° and 180°.

In the illustrated example, the tubes 43 are U-shaped tubes. The upstream and downstream ends 45 and 47 of the same tube 43 are rectilinear and parallel to each other. They are respectively substantially perpendicular to the inlet and outlet zones 35 and 37.

The curved portion 49 is formed by the central portion of the tube 43 and extends over an angular sector of 180°.

The tubes 43 are, for example, arranged in several layers superimposed on one another. Each layer, for example, includes four U-shaped tubes, parallel to each other. The four tubes have portions curved in a half-circle, with increasing respective radii. The tube with the smallest radius is situated between the two ends of the next largest tube, and so forth. Each layer is therefore substantially planar.

Preferably, the upstream ends 45 of the heat exchange tubes 43 form, with the general flow direction of the exhaust gases along the inlet zone 35, an angle comprised between 45° and 135°, still more preferably between 60° and 120°, and typically equal to 90°. Likewise, the downstream end 47 of each tube 43 forms, with the general flow direction of the exhaust gases along the outlet zone 37, an angle comprised between 45° and 135°, preferably comprised between 60° and 120°, and typically equal to 90°.

The enclosure 44 has a coolant inlet 51, a coolant outlet 53, and an unreferenced opening turned toward the valve body 7. The coolant may, for example, be heat engine coolant, air, or any other fluid.

The opening is defined by a peripheral edge that is sealably connected to the valve body 7 so as to surround the upstream and downstream zones 35, 37. The peripheral edge is, for example, alongside the side wall and brazed to that wall.

The uncovering position of the shutter element 15 is illustrated in FIG. 3. In that position, the shutter element 15 extends against the downstream zone 37. The circulation of exhaust gases is prohibited in the heat exchange tubes 43. To that end, the shutter element 15 blocks off the downstream end 47 of the heat exchange tubes 43. Alternatively, the shutter element 15 may block off the upstream ends 45 of the heat exchange tubes.

The assembly of the heat recuperation device will now be described.

The tubes 43 are first mounted on the half-shell 27. They are welded to the side wall 39 (FIG. 5), for example, by laser welding or by brazing. The enclosure 44 is then assembled on the outside of the half-shell 27, and for example brazed thereto. The shutter element 15, the axle 17 and the guide bearings 19 of the axle 17 are then assembled on the half-shell 27, and their position is adjusted such that satisfactory sealing is obtained in the uncovering position. Next, the guide bearings 19 are rigidly fixed to the half-shell 27, which guarantees sealed closure of the heat exchange tubes 43 in the uncovering position of the shutter element 15.

The frame 31 is then mounted inside the half-shell 27, as shown in FIG. 3. Its position is adjusted to obtain good sealing between the frame 31 and the shutter element 15 in the blocking off position of the shutter element 15. The frame 31 is then rigidly fixed to the half-shell 27. Lastly, the half-shell 25 is attached on the half-shell 27 and is, for example, welded thereon.

The operation of the heat recuperation device is as follows. When the shutter element 15 is in the uncovering position, the exhaust gases circulate directly from the inlet 9 to the outlet 11 along the passage pathway 13. The exhaust gases do not circulate in the heat exchange tubes 43, since the shutter element 15 blocks off the ends of those tubes.

On the contrary, when the shutter element 15 is switched into its blocking off position, the passage pathway 13 is completely blocked off. However, the two ends of the heat exchange tubes are free, such that the exhaust gases travel through the heat exchange tubes 43 and bypass the shutter element 15.

The exhaust gases cede a significant portion of their heat energy to the coolant circulating inside the enclosure 44 in contact with the tubes 43.

A second embodiment of the invention will now be described, in reference to FIG. 6. Only the differences between the first and second embodiments will be outlined below. Identical elements or elements performing the same function will be designated using the same references.

In this second embodiment, the heat exchanger 5 includes, in addition to the enclosure 44, an additional wall 55 completely blocking off the opening 57 of the enclosure 44 turned toward the valve body. The wall 55 is, for example, sealably welded to the peripheral edge of the opening. The wall 55 has no direct contact with the side wall 39 of the valve body 7. On the contrary, there is an interstice in all places, between the wall 55 and the side wall 39 of the valve body. As shown in FIG. 6, the upstream ends 45 of the heat exchange tubes 43 pass through the wall 55 before penetrating the inlet openings 33 of the valve body 7. Likewise, the downstream ends 47 of the heat exchange tubes 43 pass through the wall 55 before penetrating the outlet openings 36 of the valve body 7. The tubes 43 therefore pass through the interstice between the wall 55 and the side wall 39. They are sealably welded to the wall 55.

Furthermore, the device includes tabs 59 securing the enclosure 44 to the valve body 7. For example, a tab 59 secures the enclosure 44 to a zone of the valve body 7 situated near the inlet 9, and another tab 59 secures the enclosure 44 to a zone of the valve body 7 situated near the exhaust gas outlet 11. These tabs 59 react the weight of the heat exchanger 5 and transmit it to the valve body 7. Thus, the stresses created by the weight of the heat exchanger 5 in the tubes 43 are considerably reduced. The tabs 59 have a significant rigidity in the vertical direction and parallel to the upstream and downstream ends 45 and 47 of the tubes 43. However, the tabs 59 have a greater flexibility parallel to the contact plane between the two half-shells 25, 27, to allow a differential expansion between the heat exchanger 5 and the valve 3.

Alternatively, the device does not include tabs 59, the weight of the heat exchanger 5 being reacted by the tubes 43 and transmitted to the valve body 7.

In another alternative not shown, a layer of a thermally insulating material, for example silica fiber or glass fiber, is positioned in the interstice between the wall 55 and the side wall 39. The thickness of this layer is for example comprised between 2 and 5 mm.

In an alternative embodiment shown in FIG. 7, the upstream and downstream ends 45 and 47 of each heat exchange tube 43 extend in a first plane, the curved central portion 49 of the tube extending in a plane that is inclined relative to the first plane. The second plane forms an angle comprised between 30° and 90° relative to the first plane, preferably comprised between 30° and 60°.

As shown in FIG. 7, the tube 43 includes three successive bends. Following the tube 43 from its upstream end 45, the tube 43 first includes a first end 63, then a portion 64 with an orientation inclined toward the end of the axle 17 across from the crank 23, and also inclined toward the downstream end 47 of the tube 43. The second bend is then found, which corresponds to the curved central portion 49, then a portion 65 oriented toward the end of the axle 17 bearing the crank 23 and toward the downstream end 47 of the tube 43, then the third end 66, and lastly the downstream end 47. The bends 63 and 65 are symmetrical relative to the median plane of the upstream 45 and downstream 47 ends of the tube 43.

Such a shape makes it possible to impart a swirling movement to the gas that improves the heat exchanges with the coolant. In fact, as shown in FIG. 7, at the outlet of the first bend 63, the gas is pressed against the convex side of the tube. At the outlet of the second bend 49, the gas flows following a swirling movement when it passes through the third bend 66. The intensity of the swirling movement will primarily depend on the speed of the gas. The higher the speed, the more significant the swirling movement will be. The last bend 66 does not stop the swirling movement.

In order to still further improve the heat exchanges between the exhaust gases and the coolant, in an alternative embodiment in particular illustrated in FIG. 2, it is possible to provide corrugations 67 in the heat exchange tubes. These corrugations 67 are raised portions formed in the tube, and protruding toward the inside of the tube so as to increase the turbulence in the flow of the exhaust gases. The corrugations 67 may assume all types of shapes. For example, the corrugations 67 assume the form of a helical raised portion, formed on the tube. The corrugations 67 may also be formed by a plurality of raised rings distributed along the tube.

The tubes 43 may also be provided with disrupting elements. The disrupting elements are raised portions protruding toward the inside of the tube, the raised portions, for example, being substantially periodic. For example, the raised portions are formed by hammering the outside of the tube.

The heat recuperation device described above has many advantages.

Because the valve body has an inlet zone situated along the path between the inlet and the cutoff section, and an outlet zone situated along the path between the cutoff section and the outlet, the device further comprising a plurality of heat exchange tubes provided for circulation of the exhaust gases, each tube having an upstream end directly connected to the inlet zone and communicating with the passage pathway, the downstream end directly connected to the outlet zone and communicating with the passage pathway, and at least one curved portion between the upstream and downstream ends, the device is particularly compact. The space separating the upstream and downstream ends of each tube is reduced. It is thus possible to bring the exhaust gas inlet and outlet closer together and make the valve body particularly compact as well.

Furthermore, when the exhaust gases flow directly along the path between the inlet to the exhaust gas outlet, without going through the heat exchange tubes, the valve body is relatively hotter than the exchanger, and hotter than the heat exchange tubes. Differential expansion thus occurs between the valve and the heat exchanger. Because the distance between the upstream ends and the downstream ends of the heat exchange tubes is reduced, this differential expansion is moderated. It is not necessary to provide an expansion compensator at the valve or at the heat exchanger.

Because the shutter element prohibits the circulation of the exhaust gases in the heat exchange tubes in the uncovering position, there is no exhaust gas circulation in the exchanger when the device is in the “bypass” mode, i.e., when the exhaust gases circulate directly from the inlet toward the outlet of the valve body. This contributes to limiting heating of the coolant in bypass mode.

The fact that the heat exchange tubes are U-shaped gives the exhaust gases a flow that enables better heat exchanges with the coolant than if the tubes were straight.

These heat exchanges are even better if the upstream and downstream ends of the tubes extend in a first plane and the central part in a second plane that is inclined relative to the first.

Placing the axis of rotation of the shutter member near the side wall of the valve body to which the ends of the tubes are fixed makes it possible to arrange the shutter member such that it can pivot between the position blocking off the path followed by the exhaust gases and the position blocking off one end of the tubes. The device is thus simple to design, has a small number of components, and is light and compact.

In the embodiments of FIGS. 1 to 5, the device only includes three half-shell-shaped elements, i.e., the two half-shells making up the valve body, and the enclosure of the heat exchanger. These half-shells are typically forged, and their production is a major investment, in particular to produce the die punches. Minimizing the number of half-shells makes it possible to reduce the necessary investment, and allows a certain degree of flexibility in the design of the device. In fact, the modification of the valve body or the exchanger will cause a modification on a smaller number of elements of the device.

Directly attaching the enclosure of the heat exchanger on the valve body makes it possible to simplify the structure. On the contrary, when the heat exchanger has a wall turned toward the valve body and separated therefrom by an interstice, the heat isolation between the exchanger and the valve is improved. The interstice constitutes an air knife thermally isolating the two elements from one another. The heating of the coolant when the device is in bypass mode is minimized.

The heat recuperation device may have multiple alternatives.

The valve body may have several exhaust gas inlets and/or several exhaust gas outlets.

The shutter member, in the uncovering position thereof, may not cover the ends of the heat exchange tubes. For example, the shutter member may be a shutter member of the butterfly type. In that case, a low residual flow of exhaust gas may occur in the heat exchange tubes when the shutter member is in the uncovering position of the path followed by the exhaust gases inside the valve body.

The heat exchange tubes are not necessarily U-shaped, but may assume any type of form. They may each include several curved portions, connecting straight portions to each other. The upstream and downstream ends of the tubes are not necessarily parallel to each other. The ends of the tubes are also not necessarily perpendicular to the side wall of the valve body bearing the openings, but may be inclined relative to that wall. The valve body is not necessarily made up of two half-shells, but may be formed by a piece or by several tubular portions connected to each other, as long as it is possible to assemble the valve shutter member inside the valve body.

The heat exchange tubes do not necessarily have a circular section, but may advantageously have an oval section in a so-called “racetrack” shape. This shape makes it possible to increase the contact surface between the gases and water for same passage section offered to the gases inside the tube. Lastly, using such tubes, as compared to using tubes with a circular section, makes it possible to decrease the number thereof while maintaining an equal heat exchange power. This therefore makes it possible to decrease the number of connections on the half-shell 27. Decreasing the number of connections makes it possible to reduce the price of the exchanger part. The gain in terms of connection of the tubes greatly offsets the price difference between the two tube technologies. It is thus interesting to use a smaller number of more expensive, but higher performing tubes to reduce the welding work on the tubes.

As described above, using different corrugations increases the heat exchanges between the exhaust gases and the water, as well as the back pressure. Furthermore, in each layer of tubes, the inner tubes, closest to the axle of the valve, have a shorter bend allowance than the outer tubes, which are further therefrom. Thus, the back pressure of the inner tubes is weaker than that of the outer tubes. The flow rate in the outer tubes will be weaker than in the inner tubes, for an identical exhaust gas passage section. To rebalance the respective flow rates of the various tubes, very corrugated tubes should be used inside and weakly corrugated tubes outside. This is also true if racetrack-type tubes are used.

Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this disclosure. 

1. A heat recuperation device for an exhaust line, comprising: a valve body having at least one exhaust gas inlet and at least one exhaust gas outlet, the valve body inwardly defining a direct passage pathway for exhaust gases from the inlet to the outlet; a shutter element positioned in the valve body and able to move relative to the valve body at least between a blocking off position in which the shutter element blocks off a cutoff section of the direct passage pathway along which the exhaust gases pass and thereby prohibits the circulation of the exhaust gases from the inlet toward the outlet along the direct passage pathway, and an uncovering position in which the shutter element frees said cutoff section of the direct passage pathway along which the exhaust gases pass and thereby allows the circulation of the exhaust gases from the inlet toward the outlet along the direct passage pathway; wherein the valve body has an inlet zone situated along the direct passage pathway between the inlet and the cutoff section, and an outlet zone situated along the direct passage pathway between the cutoff section and the outlet; and a plurality of heat exchange tubes provided for circulation of the exhaust gases, each heat exchange tube having an upstream end connected directly to the inlet zone and communicating with the direct passage pathway, a downstream end connected directly to the outlet zone and communicating with the direct passage pathway, and at least one curved portion between the upstream and downstream ends.
 2. The device according to claim 1, wherein the shutter element prohibits the circulation of the exhaust gases in the heat exchange tubes in the uncovering position.
 3. The device according to claim 1, wherein the shutter element covers the upstream ends the heat exchange tubes or the downstream ends of the heat exchange tubes the uncovering position.
 4. The device according to claim 1, wherein the heat exchange tubes are U-shaped tubes.
 5. The device according to claim 1, wherein each heat exchange tube, the at least one curved portion covers an angular sector comprised between 90° and 225°.
 6. The device according to claim 1, wherein in each heat exchange tube the upstream and downstream ends extend in a first plane, a central part of the heat exchange tubes extending in a second plane that is inclined relative to the first plane, the second plane preferably forming an angle comprised between 30° and 90° relative to the first plane.
 7. The device according to claim 1, wherein the exhaust gases flow along the inlet and outlet zones in general respective directions, the upstream and downstream ends of the heat exchange tubes forming an angle comprised between 45° and 135° with said respective general directions.
 8. The device according to claim 1, wherein the inlet and outlet zones are situated on a same side wall of the valve body, the shutter element being rotatably mounted with respect to the valve body around an axis of rotation situated in an immediate vicinity of said side wall.
 9. The device according to claim 1, including an enclosure having a coolant inlet, a coolant outlet, and an opening turned toward the valve body, the heat exchange tubes extending in the enclosure, the opening being defined by a peripheral edge sealably connected to the valve body around the inlet and outlet zones.
 10. The device according to claim 1, including an enclosure having a coolant inlet, a coolant outlet, and an opening turned toward the valve body, and including a wall covering the opening, the wall being passed through by the heat exchange tubes and not coming into direct contact with the valve body. 